Non-invasive in nature, blood tests are the most commonly performed screening and diagnostic tests to reveal a rich amount of information of one's health state, ranging from chemistry and serology to hematology and immunohematology. Recently, disease specific cells existing in extremely low concentration in blood have been identified as new diagnostic and prognostic markers. For example, circulating tumor cells (CTCs) in peripheral blood are recognized as a critical cellular link between the primary malignant tumor and the peripheral metastases of patients with lung, prostate, colon, breast, liver, and ovarian cancers. However, current technology platforms lack the ability to reliably separate and detect rare cells in an extremely low quantity, down to 1-10 cells per billion red blood cells. As a result, there is no “gold standard” rare-event analysis method for measuring rare cells such as CTCs.
Conventional cell separation techniques including density gradient centrifugation, preferential lysis of red blood cells, ficoll-hypaque density centrifugation, porous filters and immunoaffinity chromatography, rely on size, density, rigidity and specific surface antigens to isolate desired cell subpopulations. These methods usually require laborious manual and bulk sample preparation steps, resulting in highly variable results and low sensitivity. The more recent molecular methods such as PCR-based detection, suffer from loss of live cells for other analysis.
Several rare-event imaging systems, including the rare event imaging system (REIS), fiber optic array scanning technology (FAST), and automated digital microscopy, have been developed to store images for re-examination without actual cell recovery. However, the number of cells to be evaluated to find rare cells is prohibitively large and the imaging modalities are rather cumbersome and complicated.
In comparison, lab-on-a-chip microfluidic devices have become increasingly attractive for blood analysis as they allow for gentle manipulation and precise control of microenvironment of individual cells in blood. However, none of the existing lab-on-a-chip approaches based on cell physical properties have offered reliable and rapid isolation of CTCs from the whole blood with minimal sample preparation.
Immunoaffinity cell isolation uses antibodies recognizing CTC specific surface antigens to achieve high specificity. However, the sensitivity of CTC detection is low and highly variable for clinical applications.
Although progress in the technology space has been made, in order to explore the benefits of CTCs in metastatic cancer, there is a need to develop cell sorting technologies that specifically target rare CTCs while meeting the sensitivity, purity, high throughput, live cell and automation requirements. Embodiments of the present invention are directed to meeting these needs.